I actually agree with you, that is a more interesting path to take than LOLCORRUPTION. I am simply saying that the orb excuse is right there in their laps.
The former leaves open all sorts of questions and old wounds, the biggest one IMO is the fact that Tyrande slaughtered a couple score of Maiev's Watchers and a Keeper of the Grove to free Illidan, and never had to answer for this crime in front of her people. Was never even called into question for doing it. Putting myself into the shoes of Maiev's character, this alone would make me absolutely furious for life. Add in the needless deaths of her Watchers, such as Naisha, that she brought along trying to recapture Illidan, and yes you've got one storm brewing.
Of course if you're a writer you could take the route that she was angry and upset and the orb just amplified it, too.